1. Field of the Invention
The present invention relates to an apparatus and method for persistent allocation in a wireless communication system. More particularly, the present invention relates to an apparatus and method for informing a Mobile Station (MS), which is allocated resources by persistent allocation, of changed decoding information.
2. Description of the Related Art
Many wireless communication technologies have been proposed as candidates for high speed mobile communication. Among them, the Orthogonal Frequency Division Multiplexing (OFDM) technique is presently recognized as the preferred next-generation wireless communication technology. In the future, it is expected that the OFDM technology will be used in most wireless communication technologies. At present, the OFDM technology is adopted as the standard in the Institute of Electrical and Electronics Engineers (IEEE) 802.16 Wireless Metropolitan Area Network (WMAN), which is considered a 3.5-Generation (3.5G) technology.
An IEEE 802.16 based system transmits a MAP message (i.e., a DownLink/UpLink (DL/UL) MAP message) including resource allocation information every frame. The resource allocation information is valid only at a corresponding frame. In general, a Voice over Internet Protocol (VoIP) service has a feature of transmitting a small sized packet by periods. Because a system has to support many VoIP users, a conventional method of performing resource allocation every frame is inefficient. Thus, in recent years, a persistent allocation scheme (i.e., a fixed allocation scheme) is being considered in which resources, once allocated, are valid periodically.
The persistent allocation scheme can reduce a signaling overhead that is generated by transmitting resource allocation information (or a resource allocation message) to a Mobile Station (MS) every frame. That is, a Base Station (BS) persistently allocates specific resources to the MS that provide a service of periodically generating traffic. Then, the MS can persistently use the resources allocated through the persistent allocation scheme until the resource is released. Accordingly, the BS does not have to transmit the resource allocation information for the MS every frame.
As described above, the persistent allocation scheme does not transmit additional signaling after transmitting signaling for the initial resource allocation. Thus, if there is a change of decoding information (e.g., a Modulation and Coding Scheme (MCS) level, power boosting information, etc.) for a burst periodically allocated according to the persistent allocation scheme, a BS has no way to inform an MS of the change. In one example, the BS can again transmit signaling for initial resource allocation (i.e., a persistent allocation message) to inform of changed information. However, transmitting the persistent allocation message every time to inform all MSs, which are allocated resources by the persistent allocation scheme, of changed decoding information as described above can result in a signaling overhead. Thus, there is a need for a technique to efficiently transmit changed decoding information to an MS that is allocated resources by a persistent allocation scheme.